1. Technical Field of the Invention
The present invention relates to a liquid shut-off valve device provided for, for example, a fuel tank of vehicle or the like and a differential pressure regulating valve provided for this liquid shut-off valve device, and relates to a technology for improving a sealing performance of the differential pressure regulating valve.
2. Related Art
As this kind of a liquid shut-off valve device, there has been, for example such one mounted on a fuel tank 101 of a vehicle as shown in FIG. 4.
Namely, this liquid shut-off valve 102 is arranged on an upper part of the fuel tank 101, and makes air and fuel vapor G101 in the fuel tank 101 flow into a canister 104, etc. absorbing fuel component of the fuel vapor 101 through an exhaust line 103 at a time of fueling, and prevents the fuel vapor G101 from being made to flow back to a filler port and exhausted therefrom into the atmosphere.
Moreover, when a liquid level of the fuel L101 is raised by, for example, fueling or swinging of a vehicle or when the vehicle is tilted or overturned, this liquid shut-off valve device 102 has a liquid shut-off function to prevent the fuel L101 from leaking out of the exhaust line 103.
FIGS. 5(a) and 5(b) are a cross-sectional configuration views for illustrating the constitution and its function of the liquid shut-off valve device. FIG. 5(a) shows a state allowing the fuel vapor G101 to be exhausted without exerting the liquid shut-off function, and FIG. 5(b) shows a state in which the level of the fuel L101 is raised and the liquid shutoff valve device 102 closes the valve by operating the liquid shut-off function.
In both Figures, reference mark 110 is a case member, of which an inner part is a float chamber 110a for housing a float 111. The float 111 generates a buoyant force by the fuel L101 made to flow into the float chamber 110a from a communicative hole 112a of a cap 112 mounted on a lower end of the case member 110, and is moved upward in the state of these figures.
A ring form of a sealing valve body 111a exerting a sealing performance is provided on a top portion of the float 111, and a valve seat part 110b corresponding to the valve body 111a is provided on a top portion of the float chamber 110a. Here, a valve constituted by the valve body 111a and the valve seat part 110b is defined as a float valve 105.
Moreover, reference mark 113 is a spring performing a function as an biasing means for adjusting the buoyant force of the float 111. This spring 113 is always biasing the float by a weight smaller than own weight of the float 111 and does not push up the float to shut the float valve 105 at the time there is no buoyant force in the normal condition.
The valve seat part 110b is arranged at one end of a vent part 110c, and a valve seat part 110d, to which a differential pressure regulating valve 120 is to be abutted, is open at the other end of the vent part 110c.
Therefore, an exhaust path is configured, for exhausting the fuel vapor G101 from the valve seat part 110b to the vent part 110c, and further to the exhaust line 103 via the differential pressure regulating valve 120.
Since the differential pressure regulating valve 120 is opened by an inner pressure of the fuel tank 101, in order to introduce a pressure equivalent to the atmospheric pressure (or a negative pressure) into an operating chamber R101, and operating chamber 101 is provided with a filler port 106 which is connected to a filler tube 107 (fuel filling part) via a filler line 108 (refer to FIG. 4).
And, in a state in which a differential pressure is small between a pressure in the fuel tank 101 and that in the operating chamber R101, since the differential pressure regulating valve 120 is biased by the spring 121 in the direction of opening the valve, it closes the valve seat part 110d, and when the differential pressure becomes a predetermined value or higher at a time of fueling and the like, the valve is opened to make the fuel vapor G101 flow out into the exhaust line 103.
The differential pressure regulating valve 120 has a diaphragm 120a of a rubber like elastic body, a retainer 120b being abutted to the diaphragm 120a for holding the form, and an orifice plug 122.
The diaphragm 120a and the retainer 120b are tightly fixed to each other by such a way as a projecting part 120c formed in the center part of the diaphragm 120a is engaged in an engaging hole 120d of the retainer 120b.
The orifice plug 122 has an orifice allowing a small flowing flow to communicate between the inside of the fuel tank 101 and the operating chamber R101, and is attached so as to hold the diaphragm 120 with the retainer 120b.
And, the orifice eliminates a differential pressure between those of the operating chamber R101 and the inside of the fuel tank 101 in a predetermined time to maintain a closing valve characteristic of the differential pressure regulating valve 120, or permits to exhaust the fuel to the side of the fuel tank 101 by a small amount when the fuel L101 is made to flow into the operating chamber R101.
Here, the reason for the connection between the operating chamber R101 and the filler tube 107 is to make the fuel vapor G101, which passes through the orifice 122 and the pressure film of the differential pressure regulating valve 120 (the fuel vapor G101 sometimes passes through the pressure film in a case, etc. that the pressure film is configured of a thin film comprising of a rubber elastic body), to be not directly discharged into the atmosphere, and to generate a differential pressure between the operating chamber R101 and the inside of the fuel tank 101 by making use of a negative pressure generated in the filler tub 107 at the time of fueling.
Moreover, a filler port which is an opening end of the filler tube 107 is normally closed with a cap, and the fuel vapor G101 is made resistant to be discharged out of the filler port by Venturi effect of the fuel L101 filled up at the time of fueling.
Therefore, FIG. 5 (a) shows a state in which the float 111 is stationed at a lower position due to no buoyant force exerted thereon, and when the inner pressure of the fuel tank 101 is raised by fueling, etc., the fuel vapor G101 flows into the vent part 110c from the valve body 111a in an open state and the valve seat 110b and is allowed to flow out into the exhaust line 103 by opening the differential pressure regulating valve 120 due to the differential pressure.
FIG. 5(b) shows such a state in which the liquid level L101a rises due to fueling, etc. and the fuel 101 flows into the float chamber 110a, and the float 111 is floated up to close the float valve 105 and shut off the exhaust line 103.
Then, as the liquid level L101a of the fuel L101 in the float chamber 110a drops, the float 111 also falls and resets the exhaust line 103 and the fuel tank to the normal state in which they are communicating with each other, to open the float valve 105 (the state shown in FIG. 5(a)).
FIG. 6 shows an enlarged view of the differential pressure regulating valve 120. In such a liquid shut-off valve device 102, the differential pressure regulating valve 120 is comprised of the three members of a diaphragm 120a, a retainer 120b, and an orifice plug 122 as described above.
However, since the diaphragm 120a is tightly fixed to the retainer 120b at the two points of the projecting part 120c and the orifice plug 122, a misalignment between them slightly brings wrinkles or deformations on a bead part 120e of the diaphragm 120a, leading to a decrease in its flatness and sealing performance at a time of closing the differential pressure regulating valve.
This is because the differential pressure between the operating chamber R102 and the inside of the fuel tank 101 to be set for opening the differential pressure regulating valve 120 of the liquid shut-off valve 102 is set to a small differential pressure (about 30 mmAq), therefore, a biasing force by the spring 121 is also set to be low, so it is difficult to correct the wrinkles and deformations by the load (a biasing force) of the spring 121 at a time of closing the valve and this fact makes it impossible to bring the bead part into an intimate contact state with the valve seat part 110d, influencing the sealing performance.
FIG. 7 shows a cross sectional view of an another type of conventional differential pressure regulating valve device without orifice plug. FIG. 8 shows a cross sectional view of the valve part of differential pressure regulating valve which is used in the device of FIG. 7. The diaphragm 130a has a projecting part 130c, which is placed on the center of the diaphragm, with a top bulge 130f formed on the projecting part 130c as shown in FIG. 8(a). The projecting part is inserted and fixed in an engaging hole 130d of a retainer 138b. When interference between the projecting part and the engaging hole is large, small wrinkles tend to appear in a bead part 130e of a sealing portion of the diaphragm, leading to a decrease in its flatness and sealing performance at a time of closing the differential pressure regulating valve. On the other hand, when interference between the projecting part and the engaging hole 130d is small, negative pressure on the canister side causes a tendency of a coming out of the projecting part 130c from the hole of the retainer, and the thus coming out projecting part 130c can not come back easily into the engaging hole because the projecting part can not re-enter into the engaging hole easily due to the difference between in the diameter of the bulge part 130f and in the diameter of the hole (the diameter of the bulge part 130f is larger than the diameter of the engaging hole 130d), as shown in FIG. 8(b). This phenomenon causes wrinkles or deformation on or around the bead part 130e of a sealing portion, leading to a decrease in sealing performance at a time of closing the differential pressure regulating valve.
Biasing force by the spring 131 is set to be low, so it is also difficult to correct the wrinkles and deformations by the load (an biasing force) of the spring 131 at a time of closing the valve and this makes it impossible to bring the bead part into an intimate contact state with the valve seat part 130g, causing a decrease in sealing performance, as mentioned above.